ci: Check snippets in coding style

To avoid having the coding style get out of sync with the actual
coding style in the future, run eslint on the individual snippets
when either the guide or the linter config change.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3146>

.gitlab-ci.yml

@@ -149,6 +149,21 @@ eslint:
       junit: ${LINT_LOG}
     when: always
 
+eslint-doc:
+  extends:
+    - .fdo.distribution-image@fedora
+    - .gnome-shell.fedora
+  stage: review
+  script:
+    - export NODE_PATH=$(npm root -g)
+    - ./.gitlab-ci/eslint-coding-style.sh
+  rules:
+    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
+      changes:
+        - HACKING.md
+        - .eslintrc.yml
+        - lint/*
+
 potfile_c_check:
   extends:
     - .fdo.distribution-image@fedora